1. Field of the Invention
This invention relates to an apparatus and method which are of use in the manufacture of sucker rods of the kind used in the oil industry. In particular, the invention relates to the step of preparing an end of a rod for a forging step in the making of such sucker rods.
2. Description of the Prior Art
The overall procedure for starting with steel rods (approximately 5/8 inch to 11/8 inch in diameter and 25 or 30 feet long) and converting them to seleable sucker rods is well known. It involves, at an early stage in the overall procedure (after the straightening of the as-received rods and before the remainder of the process), the forging of the ends of the rod stock to develop such customary features as the elevator button, the wrench square, the pin shoulder, and the pin. Within the present state-of-the-art, the forging step is still done non-automatically; a forgeman grasps a rod which has a suitably-heated end portion and feeds it into an upset forging machine which has a suitable number of passes (different sets of dies), usually about seven in number, into which the rod end must be suitably put, one after another, and in a usual manner of working, the forgeman has access to a foot pedal which causes the forging machine to strike a blow when the pedal is depressed, i.e., whenever the forgeman believes that he has positioned the work suitably in the next pass. With such equipment, the forging process on one end is usually completed in about 10 to 30 seconds.
Prior to the present invention, the usual practice for preparing an end of a rod for forging has involved either heating in a gas-fired furnace or heating with the use of an electrical induction coil of the channel or the horseshoe type. Either practice has disadvantages. One disadvantage which is shared by the known prior art methods and apparatus for preparing the ends of rods for upset forging in the manufacture of sucker rods is this: the equipment works upon the heating of a number of rods at a time, and the rods have a certain residence time in the heating means, with new, cold rods being added to the heating means when hot ones are withdrawn for forging. The equipment produces a heated rod, ready for forging, about very 15 to 20 seconds, and the rod must be used at that time or scrapped. If a rod with a heated end is permitted to cool without being forged, it warps. The known equipment, whether induction heating or gas firing is used, yields an operation which is paced by the heating means, rather than by the forgeman.
The gas-fired furnaces have the disadvantages that they are relatively costly to build and maintain, and that with the present price of natural gas, they are costly to operate. A gas-fired furnace requires rebuilding about every three to five years.
The induction furnaces with a channel or horseshoe coil have the disadvantages, in comparison to this invention, that they are more costly to build. They are also more costly to operate, requiring on the order of twice to four times the amount of electrical power to operate that is needed by an induction-heating apparatus of the solenoid-coil type which is used in accordance with the present invention.